Summary The Piper PA-28-140 (registration C-FYKS, serial number2825719) with an instructor pilot and student on board, departed St. John's International Airport, Newfoundland and Labrador, at 1338 Newfoundland standard time for a local instructional flight. The aircraft climbed on a southwesterly heading to 2000feet above sea level (asl). At 1343, the pilot reported leaving the control zone, which was the last radio communication from the aircraft. Air traffic control radar data showed that the aircraft then descended gradually while executing a series of 90turns. The aircraft's ground speed during the descent was between 50and 70knots. (All radar speeds are 5knots.) After the fourth turn, the aircraft's ground speed increased to 100knots. The aircraft then disappeared from radar at about 600feet asl (200feet above ground level (agl)), reappearing 37seconds later at 700feet asl (about 250feet agl). (All radar altitudes are 50feet.) The aircraft entered a tight left turn then disappeared finally from radar at 1352:10, while on a westerly heading at 70knots ground speed. The position of the last radar return coincided with the location of the accident site. The student pilot died in the crash. The instructor received serious injuries, including head injuries with post-trauma amnesia, and was not able to provide investigators with information relating to the accident. Shortly after the accident, occupants of a passing vehicle noticed the aircraft wreckage and called the 911emergency operator at 1359:51. There were no known witnesses to the accident. Ce rapport est galement disponible en franais. Other Factual Information At the time of departure, 1338 Newfoundland standard time,1 the weather at the airport was reported as follows: wind from 215Magnetic at 10knots; visibility 12statute miles; a few clouds at 3000feet above ground level (agl), with an overcast ceiling at 5500feet agl; temperature 2C; dew point -3C; and altimeter setting 29.88. While transiting out of the control zone, the aircraft would have encountered a lowering ceiling that restricted the maximum altitude of the aircraft to approximately 2000feet above sea level. After the accident, snow squalls moved through the area; however, personnel in the immediate vicinity of the accident site reported that there was no snow falling in that area prior to the accident. The instructor had a valid commercial pilot licence, with no restrictions. He had a Class Three Instructor Rating, about 1000hours of instructional time, and 1300hours total of flight time. The student pilot had 21.3hours of flight time. He had made steady progress throughout his training and had made three solo flights, totalling 2.3hours. The instructor had not flown with this student before. The chief flying instructor was aware of this, and spoke with both the student and the instructor before they departed to outline the purpose and limitations of the flight, and to assess that they were both ready for the flight. Prior to the flight, the instructor and student completed the necessary pre-flight briefings, checks and calculations. The purpose of the flight was to instruct the student on engine-out, forced -landing glide techniques, and it appears this is the sequence that was initiated. The normal method of simulating an engine-out glide is to start the procedure at 3000feet. In cold weather, full carburetor heat is applied, the throttle is retarded to 1500rpm, two notches of flap are applied, and the aircraft is trimmed for 70knots (80mph). During descent the engine is warmed by short throttle increases every 500feet. The exercise is normally concluded by 500feet agl; however, instructors may descend lower. To overshoot from the exercise, full throttle is applied, the carburetor heat is set to cold, wing flaps are retracted and a climb is initiated. The engine rpm at full throttle during recovery is normally 2400-2500rpm. It was not possible to determine if the cold-weather glide technique was used during the accident flight. The aircraft was registered for commercial operation and had a valid certificate of airworthiness. Records indicate that it was being maintained and operated in accordance with approved procedures and regulations. It was not equipped with flight data or voice recording devices, nor was it required to be by regulation. The aircraft was equipped with a DEFT1 emergency locator transmitter (ELT), which was activated by impact forces. The ELT transmission was received by overflying aircraft and the COSPAS search and rescue satellite. The weight and centre of gravity were within the approved limits at take-off. Air passing through a carburetor venturi is cooled. The cooling process can cause moisture in the air to precipitate in the form of ice, which may build up inside the venturi to the extent that a drop in engine power output results. If the ice is allowed to continue to build up, engine stoppage may occur. In an aircraft with a fixed-pitch propeller, indications of carburetor icing are a loss of engine power, indicated by a drop in rpm and engine roughness. The carburetor heat system directs heated air into the carburetor from a muff around the engine exhaust manifold. The system is more effective as an anti-icing device than as a de-icing device. The application of carburetor heat to remove ice will initially cause a further reduction in rpm and engine power. Depending on the amount of ice build-up in the carburetor, it could take a considerable amount of time to clear all the ice and regain the potential for full engine power. According to the A.I.P. Canada,2 the temperature and dew point during the accident flight were conducive to serious icing effects at any engine power setting (seeFigure1). Carburetor icing may occur at any power setting, but is more likely at low power settings. It was not possible to determine if the carburetor heat was applied during the practice glide procedure or during the subsequent flight manoeuvres. Figure1. Carburettor icing diagram from A.I.P. Canada , AIR 2.3. Note: This chart is not valid when operating on MOGAS due to its volatility. Tree strike marks show that the aircraft first struck the trees in a wings-level, nose-low attitude on a northerly heading. It then travelled about 10yards through the trees before striking the ground in a left-wing-low, 20nose-down attitude, coming to rest immediately adjacent to Cochrane Pond Road. The aircraft was torn apart during the accident sequence. All the major components and aerofoil sections were found within the wreckage trail, and all damage resulted from the crash. Flight control continuity was confirmed for all flight controls. Wing flaps were up at impact. There was some bending to one propeller blade; the other blade was unbent. The cockpit engine controls were damaged and had moved during the crash sequence. Examination of the controls at the engine found that, at impact, the throttle valve was two-thirds open, the mixture was full rich, and the carburetor heat was off. The aircraft, which had been refuelled with AVGAS the day before the accident flight, contained 33gallons of fuel prior to departure. There was a strong smell of fuel at the accident site, and fuel was recovered from both tanks and from the line leading to the carburetor. This fuel appeared clear, bright and uncontaminated. The aircraft fuel selector was found in the right fuel tank position. No ice or water was found in the carburetor; however, the temperature was above freezing after the accident and any ice would have melted and drained away before the carburetor could be examined. The carburetor heat system was damaged by the impact but was otherwise intact. The carburetor was examined at the manufacturer's facility with Transportation Safety Board of Canada (TSB) personnel in attendance; no faults were found. The engine (Lycoming O-320-E2A) was run at a test facility with a replacement carburetor attached; the engine produced rated power. The TSB Engineering Laboratory examined the aircraft's instruments, exhaust system and warning lights. An impact mark from the tachometer needle was found on the face of the engine tachometer at 1900rpm, which represents a relatively low power setting. This power setting may allow level flight at a reduced airspeed, but it would be insufficient to allow a climb. Metallurgical analysis of crushed areas of the exhaust system indicated that the exhaust stacks were below the normal cruise operating temperature, suggesting that the engine was at low power at the time of impact. Filament stretching indicated that the stall warning light was illuminated at impact.